Fuel injector and flame holder



g- 23, 1955 F. T. HOLMES ET AL 2,715,813

FUEL INJECTOR AND FLAME HOLDER 3 Sheets-Sheet 1 Filed April 14, 1952INVENTORS FREDER/ 7T LMES' ROB N E. 5 BY M YZW A TTORIVEYS 23, 1955 F.T. HOLMES ET AL FUEL INJECTOR AND FLAME HOLDER 5 Sheets-Sheet 2 FiledApril 14, 1952 IN VEN TORJ' S n H M N L H 0H m MW m l 1 03 EN ww/A m 0 YB 1955 F. HOLMES ET AL 2,715,813

FUEL INJECTOR AND FLAME HOLDER Filed April 14, 1952 3 Sheets-Sheet 3 INVEN TORS FREDERICK 7. HOLMES ROB/IV E TABER 1 Q/ZWW ATTORNEYS Unite FUELINJECTOR AND FLAME HOLDER Application April 14, 1952, Serial No. 282,144

11 Claims. (Cl. 60-356) This invention relates generally to aerialmissiles. More particularly, the invention relates to burner assembliesfor controlling the combustion of air fuel mixtures in rarnjet engines.

In the operation of ramjet engines, such as used with certain types ofaerial missiles, it has been found desirable to have a constantapplication of driving energy or thrust in order that optimum range andaccuracy can be obtained. It is, therefore, desirable that the drivingenergy be brought about by a smoothly-burning, constantly-ignited airfuel mixture which produces a substantially constant or at least asmoothly varying application of driving energy or thrust.

One of the major disadvantages heretofore found in the operation oframjet engines has been a condition of improper burning commonly knownas rough burning. Burning of this type is unsteady, irregular andvariable. This type of undesirable burning results in bursts or rapidlyvarying applications of energy so that improper as well as inadequatethrust forces occur.

It is believed that the rough burning referred to, strangely enough,results from a smooth flow of the fuel mixture. When such rough burningoccurs, the flame is not uniformly propagated and large quantities ofuncombusted fuel mixture accumulate and then burn with explosiveviolence. This violent burning may result not only in an unevenapplication of driving or thrust force, but also, in some instances, itmay damage the aerial missile itself.

Experimental investigations have indicated that smooth burning can bestbe obtained by providing turbulent flow of the air-fuel mixture at thepoint where ignition occurs. This type of flow gives a thorough mixingof the air and fuel, and thus effects rapid propagation of the flame.

Accordingly, it is one of the objects of this invention States Patent toprovide a highly eflicient burner assembly for use in a ramjet engine.

Another feature of the invention is to provide an improved device fordirecting a flame into a combustible fuel mixture in a 'ramjet engine.

Still another object of the invention is to provide an igniterarrangement for constant ignition of fuel mixtures in ramjet engines.

To provide an injector arrangement for maintaining a fuel mixture flowadjacent an igniter arrangement, is also another object of theinvention.

A further object of the invention is to provide an igniter arrangement,including a shield, for maintaining low turbulence flow of the air fuelmixture adjacent an igniter flame.

2,715,813 Patented Aug. 23, 1955 2 a ramjet engine, embodying theimproved burner assembly; F Figl. 2 is an enlarged cross-section on theline 2-2 of Fig. 3 is an axial-section on the line 3-3 of Fig. 2;

Fig. 4 is an axial-section on the line 4-4 of Fig. .2 and Fig. 5 is across-section on the line 55 of Fig. 3.

In the design of ramjet engines and the like, it is necessary todetermine the best relative positions of the pilot flames for the fuelused, the main fuel nozzle arrangement, and the fuel distributing vanesin order to create burning conditions which avoid the formation of largevolumes of unburned fuel mixtures. Unburned fuel has a tendency to burnbackward explosively when ignited,

and this results in uneven burning and possible damage or destruction ofportions of ramjet engines.

In order to overcome these disadvantages and also to effect smoothburning in the combustor of a ramjet engine, igniting or pilot flameshave been provided which burn at a constant rate. These igniting orpilot flames are placed in a comparatively quiet area, but in closeproximity to the intermingling fuel and air. structurally, the smoothburning is accomplished by the use of a novel flame holder, which ispreferably in the form of a flared baflle arrangement. This bafflearrangement includes baffle wings or rake fingers, which cause the .airand fuel streams to mingle or uniformly mix, and, in addition, providesurfaces for directing the igniting flames into the fuel mixture.

The preferred embodiment of the invention is best illustrated in thedrawing of Fig. l, which shows a ramjet engine, generally designated byreference numeral 11). This ramjet engine is usually a part of an aerialmissile, and it has its body in the form of an elongated tubular ductwhich is open at both ends A and 10B. In the forward portion of theramje't engine, there is located a diffuser usually of the'frusto-conical type. This diffuser, which is commonly referred to as aram channel, such as 12, delivers air in a substantially constantstream, as indicated by arrow 13, into a combustion chamber or combustor14.

' This combustor 14 is located in the tailpipe section 14A of the ramjetengine. In the forward portion of the tailpipe section 14A, the air andburner fuel are 1 end of the combustor 14 in tailpipe section 14A.

1 body 15 is of ogival contour.

Other objects and many of the attendant advantages Fig. l is afragmentary view partially in elevation of I This burner assembly 35includes a substantially cylindrical body 15 which is anchored to thewall 11 of the ratnjet engine by means of four strut members 16, 17, 1'8and 19. The forward or upstream end 15A of the The rearward ordownstream end 158 of body 15 is constructed with a substantially flatburner face 20, as shown best in Fig. 4. This burner face is located atthe forward or upstream end of the combustion chamber or tailpipesection .14.

As shown in Fig. 3, body 15 is provided with an axial bore 21 for thereception of a fuel injector 22. This fuel injector 22 is used fordistributing fuel into the combustion chamber 14. Injector 22 fitssnugly into bore 21. This injector 22 is provided with an axial fuelpassageway or conduit 23. The conduit 23 communicates with anotherpassageway, such as a pipe 24, located in the strut member 16 throughinlet passages 24A and 2413 in the injector 22 and body 15,respectively, for supplying liquid fuel to the burner, such as keroseneor heptane, from a tank 29 located between inner wall 11 and outer wall11A of the ramjet engine 10. This is best illustrated in Figs. 1 and 3.The outer or downstream end 22A of the injector 22 terminatessubstantially flush with the burner face 20. Injector 22 iscounter-bored in end portion 22A to form a bore 228 so as to provide anair jacket 27 between a nozzle and the burner face 20. The surface ofbore 22B is internally threaded, as shown at 22C. Nozzle 25 is connectedto the injector 22 by means of a nipple 28 which is screwed into theinternally threaded portion 22C of bore 22B. This is necessary so thatnozzle 25 will be in communication with fuel conduit 23. Various lengthsof nipples may be utilized for adjusting the position of the nozzle 25with respect to the burner face 20 for different types or amounts offuel or for various burner conditions.

The burner fuel, such as kerosene or heptane, from tank 29 is deliveredthrough passageways 24, 24A, 24B, and 23 to nozzle 25. This nozzle 25,in turn, injects the fuel into combustion chamber 14 usually in aconical spray, although other types of sprays can be utilized.

The injected fuel is ignited by a number of pilot flames 30 arranged ina spaced annular series about the injector 22.

These pilot flames 30 are preferably of the self-sustaining type, thatis, the flames 30 are fed by a mixture composed of a plurality ofconstituents. This mixture, when once ignited, will continue to burn,that is, it is self-sustaining. For example, such mixtures as (1)acetylene and oxygen, (2) hydrogen and air, and (3) chlorine and certainhydrocarbons, where one constitutent is the pilot fuel and the other asupporting medium, have been found to be highly satisfactory.

In order to have effective ignition flames, a plurality of manifolds,such as 31 and 32, are formed in the body 15 adjacent the burner face20, as shown in Figs. 3 and 4. These manifolds or cavities 31 and 32 arepreferably formed by machining annular cavities or chambers in the body15. These cavities are shown as concentrically arranged, with theinnermost cavity 31 being formed adjacent the central or axial bore 21for injector 22, while manifold cavity 32 is adjacent the exteriorportion of the body 15.

More specifically, the inner manifold cavity 31 is in the form of anannular groove, with wall surfaces 33A, 33B, and 33C of fuel injector 22and the exterior surface of the fuel injector 22. The outer manifoldcavity 32 is formed by an annular groove in body 15, the outer wall ofwhich is constituted by a sleeve 36 and wall surfaces 34A, 34B, and 34Cof fuel injector 22. Sleeve 36 is applied over a cut-away portion 37 ofbody 15, and is secured in any desired manner, such as welding, so as tobecome substantially integral therewith.

Preferably, various constituents, such as a pilot fuel and a supportingmedium, as pointed out above, are introduced into the manifold cavities31 and 32, respectively, as just described through passageways or pipes38 and 39, as best shown in Fig. 4, in struts 17 and 19. Thesepassageways are connected to sources, such as 40, which contain eitherthe pilot fuel or the supporting medium. Passageways or pipes 38 and 39are connected to suitable entrances 41 and 42 in the side of the body15. Between entrances 41 and 42 and manifold cavities 31 and 32 thereare located suitable passageways 43 and 44, such as bores within thebody 15. For simplicity, only two manifolds 31 and 32 are shown butobviously a larger number may be employed if it is desired to use morethan two pilot fuel constituents.

Referring again to Fig. 3, a plurality of jet forming passageways 45 and46, hereinafter to be called orifices, are provided between each of themanifolds 31 and 32, and the burner face 20 so that the constituentswithin the manifold cavities 31 and 32 can flow through orifices and 46to the burner face 20.

For properly utilizing the various constituents for sustaining a flame,the orifices 45 and 46 are arranged in groups, herein shown as pairs, inwhich the orifices extending from the several manifolds 31 and 32 reachthe burner face 20 in an arrangement so that the constituents flowingfrom the several manifolds 31 and 32 are commingled into a singlestream. In the paired orifices shown, each pair of orifices 45 and 46are inclined so that they converge at the burner face 20, and thestreams of constituents flowing through the separate manifolds 31 and 32impinge to provide a single jet.

In order to maintain an optimum burning condition in the vicinity of thepilot flames 30, a shield 48 is provided around the burner face andextending axially past the face 20 to provide a zone of comparativequiet where the pilot flames 30 will be substantially undisturbed by theflow of air through the ram channel or diffuser 12 or by the burner fuelflow from the injector 22. The shield 48 is preferably constructed so asto have an annular tubular body portion 50 surrounding the body 15, andextending past the burner face 20 thereof so that the shield 48, aids incontrolling the flow of air to the burner face 20. A different length ofshield 48 may be desired for different operating conditions. The tubularbody portion 50 is shown in telescoping relation to the exterior surfaceof the body 15, and is secured thereto by suitable means such as setscrews 51 which may engage spaced sockets 52 in the lateral surface ofthe burner body 15.

To assure a thorough mixing of burner fuel and air adjacent the forwardor upstream region of the combustion chamber 14, the shield 48 isfurther provided with rake fingers 55, formed on the end of the tubularbody portion 50. These rake fingers 55 produce a turbulent flow of theair being delivered through the ram channel 12, and, consequently, arapid intermixing or commingling of the main burner fuel spray 26 andthe air delivered by the ram channel 12. The rake fingers 55 are in theform of segments of a conical shell. These fingers 55 also serve asflame holders in that they provide sheltered surfaces behind which theignition flames 39 can linger, so that the flame is much more readilycommunicated to or propagated into the fuel mixture adjacent the forwardend of the combustion chamber 14. The maintenance of the constantigniter flames 30 adjacent the commingling surface of the air and fuel,and the utilization of the rake fingers 55 to carry the flame intoproximity with the air fuel mixture, produces substantially constantcombustion and therefore substantially constant delivery of propulsionenergy to the ramjet device 10.

To produce optimum shielding of the pilot flames 30 and to facilitatethe communication of flame behind the flame holding rake fingers 55, itis sometimes desirable to provide groups of the orifices 45 and 46,corresponding in number to the number of rake fingers 55, and to centereach of the groups of orifices on the center line of its correspondingrake finger 55.

Recapitulating, an aerial missile including a ramjet engine 10 and alaunching carriage means such as rockets (not shown) or the like, islaunched from a launching platform. After the launching carriage meanshas substantially spent its power the ramjet engine then furnishes thenecessary thrust to move the aerial missile along its trajectory.

The entering air stream flows through the ram channel or diffuser 12,Where velocity energy is converted to pressure energy, and it is thenmixed with the burner fuel injected therein by nozzle 25. The airstreamand the injected burner fuel are mixed together by means of the rakefingers 55. The air-fuel mixture is then ignited by flames 30 and burnedin the combustion chamber 14. The products of combustion generated, i.e., the liberated gases, are then expanded through an exit nozzlearrangement located in the furthermost portion of the tailpipe section14A at a Y 5 velocity considerably higher than the velocity of theentering air stream to furnish the thrust forces required to propet theaerial missile along its trajectory.

Obviously, many modifications and variations of the present inventionare possible in view of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be prae tieed otherwise than as specifically described.

claimed is:

'L Inan aerial missile having a body in the form of anelongated'tlibulai duct, a'dirruser and a combustor iii said duct, and aburner assembly mounted at the entrance of said combustor, said burnerassembly, comprising, a body having a burner face, at least twomanifolds in said body, a pilot fuel in one of said manifolds and asupporting medium in the other, paired orifices extending between saidmanifolds and said face to provide a plurality of pilot burners due tothe commingling of said pilot fuel and supporting medium, said bodyhaving a passage for delivery of burner fuel to said combustor.

2. In an aerial missile having a ramjet engine with a ram channel forsupplying air to a combustion chamber; in combination with a burnerassembly mounted at the exit of said ram channel, said burner assembly,comprising, a body having a burner face at its downstream end, means fordistributing burner fuel into said combustion chamber, and pilot flamemeans for maintaining a plurality of pilot flames around saiddistribution means and at said burner face, said pilot flame means beingconstituted by a plurality of manifolds located in the body of theburner assembly, at least one of said manifolds containing a pilot fueland another a supporting medium, and a plurality of orifices betweeneach of said manifolds and said burner face, said orifices beingarranged in a plurality of groups, each group including an orifice fromeach manifold.

3. In an aerial missile having a ramjet engine with a ram channel forsupplying air to a combustion chamber; in combination with a burnerassembly mountedat the exit of said ram channel, said burner assembly,comprising, a body having a burner face at its downstream end, means fordistributing burner fuel into said combustion chamber, pilot flame meansfor maintaining a plurality of pilot flames around said distributionmeans and at said burner face, said pilot flame means being constitutedby 1- a plurality of concentric and annular manifolds located in thebody of said burner assembly, at least one of said manifolds containinga pilot fuel and another a supporting medium, a plurality of orificesbetween each of said manifolds and said burner face, said orifices beingarranged in a plurality of groups, each group including an orifice fromeach manifold, and a plurality of rake fingers secured to said body andextending in an outwardly flaring relation to said burner face.

4. A burner arrangement, comprising, a body having a i 7 centralpassageway extending from one end thereof along a portion of its axis,manifolds arranged concentrically and annularly about said passagewayand having paired orifices in the walls thereof adjacent that end ofsaid body having the opening therein, at least one of said manifoldsarranged to contain a pilot fuel and another a supporting medium, aseparate passageway connected to each of said manifolds and to saidcentral passageway, a fuel injection nozzle detachably mounted in theopen end of said central passageway and a shield slidably mounted onsaid body for shielding said orifices.

5. The arrangement set forth in claim 4, wherein said shield comprises afrusto-conical skirt divided into a plurality of fingers which arealigned with said orifices.

6. In an aerial missile of the ramjet type having a ram channeldelivering an air stream to a combustion chamber, a burner assemblymounted in said ram channel in the flow path of the air stream, thedownstream end of said assembly constituting a burner face, saidassembly having a plurality of concentric manifolds therein, pas- 6sageways connected to said manifolds for delivering a pilot fuel to atleast one of said manifolds and a supporting medium to another, saidassembly having a plurality" burner face.

7. In an aerial missile of the ramjet type having a ram channeldelivering an air stream to a combustion chamber, a burner assembly,comprising, pilot flame means mounted in said ram channel in the flowpath of the air stream, the downstream end of the said pilot flame meansconstituting a burner face, said pilot flame means having a pair ofconcentric, annular manifolds therein, means connected to said manifoldsfor delivering at least a pilot fire! to one of said manifolds and asupporting medium to another, said pilot flame means having a pluralityof paired orifices extending from said burner face to the respectivemanifolds, said orifices converging toward each other to provideimpinging jets of said pilot fuel and said s;:pporting medium to form aring of pilot flame when ignited, and shielding means surrounding saidburner face and including a plurality of diverging rake fingers.

8. In an aerial missile of the ramjet type having a ram channeldelivering air into a combustion chamber, a

urncr assembly, comprising, a body having a burner face defining theforward end of said combustion chamber, means defining manifolds in saidbody at least one of said manifolds arranged to contain a pilot fuel andanother a supporting medium, there being a plurality of paired oriicesextending between said manifolds and said burner face to provide aplurality of pilot flames, means for delivering a burner fuel streamadjacent said burner face, and shielding means adjacent said pilotflames.

9. A burner assembly comprising, a body having a burner face, said bodyhaving a plurality of concentric manifolds therein, at least one of saidmanifolds arranged to contain a pilot fuel and another a supportingmedium, there being a plurality of orifices in each of said manifolds,said orifices being arranged in proximity to provide a plurality ofcommingling jets of said pilot fuel and supporting medium, noule meansdirecting a fuel spray adjacent said pilot flames, and shielding meanssurrounding said body.

10. In an aerial missile of the ramjet type having a ram channel and acombustion chamber, a burner assembly located in said ram channel at theforward end of said combustion chamber, said assembly, comprising, abody secured substantially axially in said ram channel, said body havingan axial passageway therein, means for sugpiying burner fuel throughsaid passageway into said combustion chamber, a plurality of manifoldsin saidbody, passageways for supplying a pilot fuel to at least one ofsaid manifolds and a supporting medium to another, there being aplurality of outlet orifices in each oisaid manifolds, the orificesbeing arranged in a plurality of groups, each group includingan orificefrom each, manifold, the orifices of a group being arranged so that saidpilot fuel and supporting medium from the several manifolds areintermingled to sustain pilot flames, a shield about said pilot flames,and a plurality of outwardly flaring rake fingers extending from saidshield in annular arrangement about said body.

11. In combination, with a ramjet type of aerial missile having a ramchannel supplying a stream of air to a combustion chamber, a burnerassembly, comprising, a substantially cylindrical body secured axiallyin said ram channel adjacent the upstream end of said combustionchamber, the downstream end of said body constituting a burner face,said body having an axial passage terminating at said burner face, meansfor delivering burner fuel through said axial passage, nozzle meansconnected to said axial passage in proximity to said burner face fordelivering said burner fuel from said axial passage into said combustionchamber, a pair of manifolds around said axial passage, one of saidmanifolds containing a pilot fuel and the other a supporting medium,there being a plurality of pairs of pilot flame orifices in said burnerface connected to said manifolds to provide streams of said pilot fueland supporting medium therefor, shielding means around said bodyextending axially beyond said burner face to provide a shielded areaadjacent said pilot orifices, and a plurality of rake fingers formedonsaid shield and extending in divergent frusto-conical relation to saidburner face.

References Cited in the file of this patent UNITED STATES PATENTS1,924,400 Forney Aug. 29, 1933 2,214,568 Thomas Sept. 10, 1940 2,439,554Anderson Apr. 13, 1948 2,518,000 Goddard Aug. 8, 1950 2,547,936 GrowApr. 19, 1951 2,618,928 Nathan Nov. 25, 1952

